The invention relates to a fan used to exhaust heat generated, for example, in an enclosure for electronic equipment.
In electronic equipment in which a large number of electronic parts are housed in a relatively small enclosure, such as personal computers, copy machines or other office automation equipment, the heat generated by the above electronic parts builds up in the enclosure, and there is a danger of heat induced failure of the electronic parts.
Air passages are therefore provided on the walls or top surfaces of electronic equipment enclosures, allowing the heat inside such enclosures to be exhausted to the outside by installing a fan in those air passages.
A conventional fan of this type is shown in FIGS. 4 and 5. FIG. 4 is a vertical section of the conventional fan. FIG. 5 is a left side view of FIG. 4. FIG. 4 shows a linear section along the line that connects the points C-O-D in FIG. 5. In both figures, reference number 1 designates a casing, with an air passage hole 1a formed in the center portion thereof. A motor base 4 is affixed in the center portion of the air passage hole 1a in the casing 1 by means of three ribs 3 which extend from the opening edge of the air passage hole 1a. A cylindrical bearing holder 5 is affixed in the center portion of the motor base 4. The outer rings of bearings 6 and 7 are mounted on the inside of the cylindrical bearing holder 5, and a motor rotation shaft 8 is inserted in and supported by the inner rings of the bearings 6 and 7. An impeller 10 comprises five blades 10d on the outer perimeter of an impeller main unit 10c having a cylindrical section 10a and a boss portion 10b. The impeller is joined to the top end of the motor rotation shaft 8. Blades 10d rotate around the shaft's axis as the shaft 8 rotates. A motor yoke 13 is mounted inside the impeller cylindrical section 10a, and a cylindrical permanent magnet 14 is affixed to the inner perimeter of the motor yoke 13. A stator winding 15 and iron core 16, are affixed to the outside of the bearing holder 5. Along with the motor yoke 13 and permanent magnet 14, the stator winding and the iron core form the main components of direct current motor DCM. A PC board 17 is attached to the stator iron core 16 in order to provide a specified current to the stator winding 15. This causes the stator winding 15, iron core 16, motor yoke 13 and permanent magnet 14 to operate as a brushless direct current motor DCM. On the motor base 4, the center axis 4a has an annular outer wall 4b positioned concentrically to the shaft 8. As shown in FIG. 4, the two edge surfaces of the ring-shaped outer wall 4b have the same diameter measurement, thus forming a cylinder. The fan described above is attached to the air passage holes in an office automation equipment enclosure.
When a direct current power source is supplied to the attached fan, a current controlled by the PC board 17 flows to stator winding 15, a magnetic flux is generated from the stator iron core 16, and the motor yoke 13 and blades 10d rotate due to the mutual magnetic effect of the stator iron core and the permanent magnet 14. As a result, air on the right side of the motor shown in FIG. 4 is pulled in and then is exhausted out of the left side of the motor shown in this figure, passing through the air passage hole 1a. Cooling of the enclosure interior is accomplished by this fan action.
A satisfactory air flow volume can to some extent be obtained even using such conventional technology as described above, but even a slight increase in air flow volume means a large effect in exhausting heat generated in electronic equipment enclosures to the outside.